The dilution rate was kept constant (I:2),and the num-
ber of spermatozoa o{ each dose of volume 0.Iml ranged
between I00 & I50XIO" ,Only semen of high initial den-
sity and motility was used,

RESULTS & DISCUSION,The onset of oestrus occurred wi-
thin an interval of two to three days after the last
progesterone injection and was general in all the indi-
viduals of groups A,B & C,with the exception of one ewe
of group A,which,although having vaginal oestrus,did not
exhibit any behavioural oestrus,.On the contrary,none of
the 30 ewes of the control group M showed any sign of
oestrus during the above period,Figure I/A illustrates
the time of appearance of the oestrus in groups A,B & C
in comparison to control group M,(Fig.I/C),in which the
normal oestrus cycles delayed about 35 days,were spread
over a period of about 60 days,

The interval between the last progesterone injection
and the onset of oestrus ranged between L5 & 80 hours,
The duration of the induced oestrus also fluctuated bet-
ween.16 and 63 hours.,From data of table I,it is conclu-
ded that the differences among the experimental groups,
with regard to the interval between the last progeste~
rone injection and the onset of oestrus,were not signi-
ficant.However,the difference as regards the duration
of oestrus was significant between groups A & C#P{0.0I).
This agree with the results obtained by Lamond 3),who,
in an experiment with Merino ewes,which were injected
with 400,I200 & 3600i,u.of PMS,after a I4-day progeste-
rone treatment,induced oestrus durations averaging 26,
36 & 76 hours respectively,

It is characteristic that the only ewe which although
did not exhibit behavioural oestrus conceived,belonged
to group A,This is in accordance with Robinson's find-
ing(7),that a PMS dose of less than I000i,.u,,although
sufficient to induce ovulation produces only marginal
quantities of oestrogen in the organismjthus "silent
heat"or"ovulation without oestrus"(4),may sometimes ap-
pear.,As it is illustrated in Fig.,I/B,out the I3 ewes
which did not conceive during the first post-treatment
oestrus,the I2 had their next oestrus cycles spead over
a period of 35 to 50 days.This is in contrast with Lam-
bourne (2),who gave evidence that hormonal treatment
applied six weeks before the end of the anoestrus period
resulted in:a series of successive oestrus cycles of
normal duration.,As it is shown in Table 2,the conception
rate was quite different between the experimental groups,
On the other hand,from the data of Table 3,it is suggest-
ed that a relation may exist between the duration of oe-
strus and the conception rate.Only individuals exhibi-
ting normal oestrus duration,irrespective of group,con-

 

 
  

 

  

1484